- Interconnections between species
- The flow and cycling of resources (energy and nutrients) in ecosystems
- Ecosystem responses to disturbance
Students should be able to...
- ANALYZE changes in an ecosystem.
- REPRESENT energy flow through an ecosystem, as in an energy pyramid.
- DISTINGUISH accommodation within individuals from genetic adaptation in a population. (I'm saving this for Unit 3 when we get into evolution.)
- DETERMINE the fluctuations in population size caused by birth, immigration, emigration, and death.
Students should understand that...
- Ecosystems include a variety of different roles that can interact in complex ways. (Big Idea #1)
- Both negative interactions (competition, predation) and positive interactions (cooperation, mutualism) are important in shaping the structure of ecological communities. (#1)
- Different species use different survival strategies, which can be successful in very different ways (e.g., r-selection vs. K-selection; Type I, II and III survival curves).
- Species' populations can be regulated from the "bottom up" (by resource limitation) or from the "top down" (by predation and disease). (#1, #2)
- Nutrients cycle within the biosphere: carbon, nitrogen, oxygen, and water are reused again and again, with little "new" input or loss (though human CO2 production is a major exception!). (#2)
- Ecosystems are open-ended with respect to energy: producers obtain it from one source (almost always the sun) and pass it up the food chain, losing some energy to heat at every step. (#2)
- Some ecosystems depend on "keystone species", and that threatening these species threatens the entire structure of the community. (#3)
- Outside disturbance can upset the balance of an ecosystem, and that the degree of upset depends on both the magnitude of the disturbance and the robustness of the ecosystem. (#3)
- How are different species dependent on each other?
- Why is preserving biodiversity important?
- What makes an ecosystem stable or vulnerable?
- How do resource needs constrain the structure of ecological communities?
- How can we protect ecosystems from damage, and when should we do so?
- Have students plot the flow of resources and/or interaction webs in sample ecosystems.
- Write the "biography of a nitrogen atom" (or a carbon atom, etc.) as it journeys through its nutrient cycle.
- Examine population data to determine if a species is at its carrying capacity in a particular ecosystem.
- Identify populations that are under "bottom-up" or "top-down" regulation.
- Study real-world systems where dramatic shifts have occurred in community structure, and identify likely causes for the change.
- Research an exotic species that has been introduced to California (chosen from a list) and present a report explaining whether it has become invasive, how they can tell, and what is being done to combat it (if anything).